No one seems to have made a list, though someone should have. The first thing to say is that most tpers can understand a variety of styles. The second is that they are not slow to "correct" what differs from their own preference. On the other hand, most of the things that get corrected now are the same things that got corrected in the early days. There haven't been many changes and the essentials remain-- and remain unfamiliar to beginners. But let's see.1. There are half a dozen words that are not in the pu vocab or are listed as alternates which are considered fully functional. Check older lists for their meanings and uses.2. 'pi' indicates a unit block within a string of modifiers, a break in the left grouping of each successive word. It is not a possessive marker. It cannot be followed by just one word (obviously).3. 'kepeken' is a preposition, so, like all preposition, wherever it occurs, it's complement, the tool, follows immediately, without 'e'.4. To speak a language X is 'toki kepeken toki X' or 'toki lon toki X'. To talk about X, is 'toki e ijo (pi) X'. I'm sure there are more but these are the ones that turn up most. and they are not all that different from pu (a word that is not much used).

Oh, yes5. Prepositional phrases can modify nouns, but (see above) must be introduced by 'pi'.6. The only multi word modifiers that do not take 'pi' are numbers or 'nanpa' followed by a number. (The verdict is pending on reduplication for emphasis.)

Something like this usage, though not quite this justification, existed in very early tp and left some traces in Pije's lessons (he once uses 'pi' for "have"). This was a minor role already in those lessons and dropped out completely in later usage. This list is an attempt to report current standards, so this usage does not have a place. The "obviously" referred to the context of right grouping, where one word would not fit. Arguably, Egyptian gods are 'jan soweli sewi' and gods for animals, if not 'soweli sewi', are 'jan sewi soweli', given the standard ordering of modifiers.